Translation:They cannot go because of the rain.
"They can't go because it's raining" is an acceptable translation, or is the meaning not quite the same?
I think your answer should be accepted as well.
"They cannot go because of the rain."
"They can't go because it's raining."
According to me, the only difference between these two English sentences is that the second one uses the present continuous.
I think this implies that it is still raining right now (ongoing action).
The Indonesian sentence can also be interpreted as an ongoing action.
It's not specifically mentioned that it's still raining, but it certainly doesn't rule out this possibility.
The formal marker for continuous action is "sedang"
"Saya sedang mencuri dompet dia" = "I am stealing her wallet"
In informal language, this is replaced with "lagi"
"Aku lagi nyuri dompetnya"
"Terus" and "Masih" can also be used to describe ongoing actions. I'd translate them as "continues to" and "still" respectively, but I don't have that great of an understanding of their use, especially terus.